"We're sitting on a bomb," says Azevedo, safety officer for Brazilian company Petrobras's Cidade de Itaguai platform, about 150 miles (240 kilometers) off the coast of Rio de Janeiro.

At 28, Azevedo is responsible for enforcing rules designed to prevent everything from platform crew members falling down stairs to the entire place blowing up.

And the prospect of a platform turning into a fireball while sucking oil out from miles under the ocean floor is not an altogether unreasonable fear.

The platform -- actually a converted oil tanker -- is crammed with high-pressure networks of oil and natural gas lines, not to mention the 1.6 million barrels of oil it stores in its hold.

"A gas leak could provoke an explosion... with very serious fatalities," Azevedo says, when asked his greatest concern.

Anchored in sometime stormy waters 7,350 feet (2,240 meters) deep, the Cidade de Itaguai platform defies nature's most primal forces -- and what until recently were considered humankind's own limitations.

- Almost science fiction -

Employees working inside the high-tech control room of the Cidade de Itaguai oil platform off the Brazilian coast

The rewards, say Petrobras and its growing list of foreign partners in the pre-salt project, are just as impressive.

For example, the Lula field, where the platform is located, has an estimated 8.3 billion barrels of reserves, making it by far the most important part of the Santos basin, which now accounts for 40 percent of all oil production in Brazil. Lula alone produces close to 800,000 barrels a day.

To get at those riches, the Cidade de Itaguai pumps oil from seven wells piercing not just 1.4 miles (2.2 kilometers) underwater but a further 3.1 miles (five kilometers) below the seabed.

Until a decade ago, this was almost science fiction. Even now, such operations are reserved for the world's oil majors.

"The equipment is getting bigger and with that, so are the complications," said Johan Vermaak, 46, the South African who manages the platform. "This is groundbreaking what's happening here."

- Claustrophobic conditions -

Transportation to and from the oil platform depends on helicopters, with employees shuttled ashore every two weeks

MAURO PIMENTEL, AFP

Travel to and from the platform, including during a rare visit by AFP and three Brazilian media outlets, is dependent on helicopters.

From the air, the Cidade de Itaguai looks like some mad scientist's creation -- an otherwise ordinary ship festooned in so many yellow and white pipes and so much scaffolding that there appears to be no space left to move.

The platform is seven stories high, and has a deck area equivalent to three football fields, so the 150 crew spend much of their lives navigating steep staircases and long, windowless corridors.

Although the ship, held in place by 24 mammoth anchors, is in mid-ocean, most of its exterior work stations barely have a view of the water. Once inside, there's only the slight swaying of the hull in the waves to remind you of the sea at all.

Petrobras contracts Tokyo-based Modec to run the installation, with a crew drawn 85 percent from Brazil, plus others from as far afield as India, Italy, Malaysia and Ukraine.

Most crew members work two weeks straight, then fly back to shore for a two-week break. While aboard, they sleep in bunks in small, plain cabins where a hot shower and a television are the only frills.

There are two phone booths for calls home, a small room for video games, an equally tiny gym, and a canteen with a meat-heavy menu. In the row of recycling bins, one is marked: "Only bones."

Between the long work hours, limited entertainment, tight spaces, alcohol ban and a multitude of rules, claustrophobia is a more common problem than physical injury.

"We're confined here. We're miles away from the coast and that's in addition to the whole operational context, which is already stressful," said Vinicius Ferreira, the ship's medic.

- Future or bust? -

Another aerial view of the Cidade de Itaguai oil platform, with its heliport occupying one end of its incredibly crowded deck

MAURO PIMENTEL, AFP/File

Every day, 150,000 barrels of oil are pulled up through a row of pipes hanging from the side of the ship, sent to the treatment complex on deck, and then stored.

As often as twice a week, tankers tie up to the platform to take deliveries, the oil gushing through what is basically a mammoth hose. And even as the cargo ship takes its load, Cidade de Itaguai continues to draw fresh oil from underground.

The pace is relentless.

Petrobras, an iconic Brazilian state company that has been badly damaged by a corruption scandal and the sharp global decline in oil prices, is betting big on pre-salt.

Today, the Santos basin produces 1.15 million barrels a day. By 2021, the Brazilian oil agency says the basin's production will almost double to 2.1 million bpd.

But with oil prices down and alternative energies on the rise, Vermaak, an offshore industry veteran, wonders if pre-salt will be not the new frontier, but the finishing line.

"I would imagine this could be the end stretch," he said.

To the men and the handful of women on Cidade de Itaguai, such longterm considerations are immaterial. Their focus is simpler: getting the oil safely out today and getting home tomorrow.

Asked the first thing on his mind when he boards that helicopter on shore leave, Vermaak roared with laughter.